Iraqi security forces guard at the site of a bomb blast at Baghdad's northern Azamiyah neighborhood, Iraq, Sunday, Sept. 15, 2013. As a few car bombs hit cities in southern Iraq, a blast targeting the head of Baghdad's provincial council in the capital's northern Azamiyah neighborhood killed at least two and wounded at least eight, police say. The council head escaped unharmed. (AP Photo/Khalid Mohammed)— AP

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Iraqi security forces guard at the site of a bomb blast at Baghdad's northern Azamiyah neighborhood, Iraq, Sunday, Sept. 15, 2013. As a few car bombs hit cities in southern Iraq, a blast targeting the head of Baghdad's provincial council in the capital's northern Azamiyah neighborhood killed at least two and wounded at least eight, police say. The council head escaped unharmed. (AP Photo/Khalid Mohammed)
/ AP

An Iraqi boy rides his bicycle at the site of a car bomb attack at the town of Suwayrah, 25 miles (40 kilometers) south of Baghdad, Iraq, Sunday, Sept. 15, 2013. A new wave of insurgent attacks, mostly car bombs targeting Shiite-dominated cities in central and southern Iraq, killed and wounded scores of people, officials said. (AP Photo/Hadi Mizban)— AP

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An Iraqi boy rides his bicycle at the site of a car bomb attack at the town of Suwayrah, 25 miles (40 kilometers) south of Baghdad, Iraq, Sunday, Sept. 15, 2013. A new wave of insurgent attacks, mostly car bombs targeting Shiite-dominated cities in central and southern Iraq, killed and wounded scores of people, officials said. (AP Photo/Hadi Mizban)
/ AP

Policemen inspect the site of a car bomb attack in front of the headquarters of the Police Quick Reaction Force in the town of Suwayrah, 25 miles (40 kilometers) south of Baghdad, Iraq, Sunday, Sept. 15, 2013. A new wave of insurgent attacks, mostly car bombs targeting Shiite-dominated cities in central and southern Iraq, killed and wounded scores of people, officials said. (AP Photo/Hadi Mizban)— AP

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Policemen inspect the site of a car bomb attack in front of the headquarters of the Police Quick Reaction Force in the town of Suwayrah, 25 miles (40 kilometers) south of Baghdad, Iraq, Sunday, Sept. 15, 2013. A new wave of insurgent attacks, mostly car bombs targeting Shiite-dominated cities in central and southern Iraq, killed and wounded scores of people, officials said. (AP Photo/Hadi Mizban)
/ AP

Officers of Police Quick Reaction Force inspect the site of a car bomb attack in front of their headquarters in the town of Suwayrah, 25 miles (40 kilometers) south of Baghdad, Iraq, Sunday, Sept. 15, 2013. A new wave of insurgent attacks, mostly car bombs targeting Shiite-dominated cities in central and southern Iraq, killed and wounded scores of people, officials said. (AP Photo/Hadi Mizban)— AP

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Officers of Police Quick Reaction Force inspect the site of a car bomb attack in front of their headquarters in the town of Suwayrah, 25 miles (40 kilometers) south of Baghdad, Iraq, Sunday, Sept. 15, 2013. A new wave of insurgent attacks, mostly car bombs targeting Shiite-dominated cities in central and southern Iraq, killed and wounded scores of people, officials said. (AP Photo/Hadi Mizban)
/ AP

A policeman guards next to a damaged armored sport utility vehicle following a bomb blast at Baghdad's northern Azamiyah neighborhood, Iraq, Sunday, Sept. 15, 2013. A blast targeting the head of Baghdad's provincial council in the capital's northern Azamiyah neighborhood killed at least two and wounded at least eight, police say. The council head escaped unharmed. (AP Photo/Khalid Mohammed)— AP

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A policeman guards next to a damaged armored sport utility vehicle following a bomb blast at Baghdad's northern Azamiyah neighborhood, Iraq, Sunday, Sept. 15, 2013. A blast targeting the head of Baghdad's provincial council in the capital's northern Azamiyah neighborhood killed at least two and wounded at least eight, police say. The council head escaped unharmed. (AP Photo/Khalid Mohammed)
/ AP

BAGHDAD 
A wave of car bombings and other attacks in Iraq killed at least 53 people in mostly Shiite-majority cities on Sunday, another bloody reminder of the government's failure to stem the surge of violence that is feeding sectarian tensions.

Iraq is experiencing its deadliest bout of violence since 2008, raising fears the country is returning to a period of widespread killing such as that which pushed it to the brink of civil war following the 2003 U.S.-led invasion. More than 4,000 people have been killed in attacks since the start of April, including 804 just in August, according to United Nations figures.

Sunday's deadliest attack was in the city of Hillah, 95 kilometers (60 miles) south of Baghdad, where a car bomb near an outdoor market killed nine civilians and wounded 15 others, a police officer said. A few minutes later, another car bomb went off nearby, killing six civilians and wounding 14, he added.

In the nearby town of Iskandariyah, 50 kilometers (30 miles) south of the capital, another car bomb hit a parking lot, killing four civilians and wounding nine, police said.

Another car bomb went off in an industrial area of the Shiite city of Karbala, killing five and wounding 25, a police officer said. Karbala is 80 kilometers (50 miles) south of Baghdad. In the aftermath, security officials inspected burnt-out cars in front of what appeared to be a smashed row of workshops.

Seven more civilians were killed and 31 others were wounded when four separate car bombs ripped through the towns of Suwayrah and Hafriyah outside Kut, police said.

In Baghdad's northern Sunni-dominated Azamiyah neighborhood, a car bomb that exploded near the convoy of the head of Baghdad's provincial council killed three and wounded eight, police say. The council head escaped unharmed.

Two other car bombs hit the southern cities of Basra and Nasiriyah, killing eight civilians and wounding 26, two police officers said. And two more civilians were killed when a bomb hit a police patrol in Baghdad's Sunni western suburb of Abu Ghraib. Nine other people were wounded.

To the northeast of Baghdad, gunmen broke into a farm in the village of Abu Sayda and killed three Sunni farmers, police said

No one has claimed responsibility for the blasts, which targeted commercial areas and parking lots in seven cities. But systematically organized waves of bombings are often used by al-Qaida's local branch, known as the Islamic State of Iraq, to undermine confidence in the Shiite-led government.

Sometimes insurgents launch multiple attacks for two or more days in a row. On Saturday, 27 people were killed in suicide attacks, bombings and shootings.

In the afternoon, police found the bodies of four Sunni men killed with gunshots to the head. The men, all relatives, were kidnapped early Sunday by gunmen who stormed their house in Baghdad's southern Youssifiyah suburb.